1. Field of the Invention
The present invention relates to a projection welding structure.
2. Description of the Related Art
Projection welding is known for welding a welded member to welding projections (projections) formed as welding portions to a welding member (base member) by passing current through the welding projections whilst pressing the welded member onto the welding projections (for example, Japanese Patent Laid-Open (JP-A) No. 9-57462). In the technology described in JP-A No. 9-57462 a plate shaped welding member formed with plural welding projections is superimposed on and projection welded to a plate shaped welded member. A support face of an electrode that supports the welded member is formed with plural recessed portions each corresponding to the respective welding projections, and locations of the welded member pressed by the welding projections are capable of elastic deformation (for example bowing) into the recessed portions. Tolerance (variation) between heights of the respective welding projections is accordingly accommodated, and electrical current is suppressed from being concentrated on particular welding projections.
However, there is a possibility of the welding face of the welding member making contact with the welding face of the welded member at locations other than the welding projections prior to completing welding of the welded member to the welding projections, for example as a result of manufacturing errors in for example the welding face of the welding member or the welded member, or the support faces of electrodes. The electrical current splits at contact locations other than the welding projections in such cases, causing poor welding due to a decrease in the amount of current flowing in the welding projections.